Heat the butter and jam in a saucepan and stir. Crumble the biscuits in a food processor or place in a plastic bag (do not close) and crumble with a rolling pin. Mix the biscuits with the butter-jam mixture. Spread the mixture over the base of the springform pan and press firmly with a spoon. Allow to cool in the fridge for 10 min. Use a mixer to lightly beat the cream cheese and sugar. Beat the whipped cream with the whipped cream stabiliser and vanilla sugar and mix in the cream cheese. Spread the mixture over the tart crust. Finally, cover with the flan filling. Allow the tart to set in the fridge for at least 2 hours.